thanks for the quick response, Watermom. I'm hoping the water will clear on its own - seems a bit clearer than yesterday, but that may be wishful thinking.

I've been using AquaChek strips to monitor pH & chlorine, with pool store tests a few times a year. Right now the strip says free chlorine is 5 ppm; pH is 7.8; alkalinity is about 150; stablilizer is 30-50 -- all good.
This is a 100,000 litre vinyl pool filled with city water. I have a Pentair Clean&Clear cartridge filter and a 1hp hayward pump running 12 hrs/day. (I did fill out the pool chart, but I just joined this forum today & don't seem to be able to see it again.)
This year, all I've added is chlorine (hth ultra & pucks in the chlorinator); sodium bicarb (Alka-plus), and now the Phos-free.
My pump is 1 hp, run 12 hrs/day.